On 10 February 2016 at 15:50, Joel C. Ewing <[email protected]> wrote: >> Why do you think that SIE would not continue to provide virtual >> ESA/390 support? Today, when z/VM is running in zArch mode on the >> metal on e.g. a z12, it can surely have an ESA/390 mode guest OS. I >> see no reason that wouldn't continue just because the host processor >> doesn't IPL in ESA/390 mode. >> >> Tony H. >> >> > Well that was sort of my first thought too, but the actual wording in > z/VM Statement of Direction was that "the IBM z13 server family will be > the last to support ESA/390 architecture mode", not that it wouldn't > support ESA/390 mode on IPL. That sure sounds like there will no longer > be any hardware ability to switch ARCHLVL mode, and that z14 and later > will run only in ARCHLVL2 mode.
Well I don't know what IBM has actually said, or what they mean, so I'm speculating as much as you are. Hopefully one of our friendly IBMers will step in and clarify. But my understanding of "the IBM z13 server family will be the last to support ESA/390 architecture mode" is simply that on z14+ the IPL sequence will not start in or pass through ESA/390 mode, and it will not be possible to issue a SIGP to set ESA/390 mode. OK, but none of this suggests that a guest under SIE will not be able to run in ESA/390 mode. Perhaps the IPL will take some assistance from z/VM, but no one cares if that has high emulation overhead. BTW, this whole "switch architecture modes on the fly" reminds me of the famous Gordon Letwin "turning the ignition off and back on when the car's doing 60 MPH" scheme for the Intel 286 on OS/2. Only it's architected, rather than being a fortuitous kludge. http://www.google.com/patents/US4825358 Tony H. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
